I. Field of the Invention
The present invention relates to techniques for semiconductor processing, and more particularly to semiconductor processing which may be performed at low temperatures.
II. Description of the Related Art
In the field of semiconductor processing, there have been several attempts to use lasers to convert thin amorphous silicon films into polycrystalline films. For example, in James Im et al., “Crystalline Si Films for Integrated Active-Matrix Liquid-Crystal Displays,” 11 MRS Bullitin 39 (1996), an overview of conventional excimer laser annealing technology is presented. In such a system, an excimer laser beam is shaped into a long beam which is typically up to 30 cm long and 500 micrometers or greater in width. The shaped beam is scanned over a sample of amorphous silicon to facilitate melting thereof and the formation of polycrystalline silicon upon resolidification of the sample.
The use of conventional excimer laser annealing technology to generate polycrystalline silicon is problematic for several reasons. First, the polycrystalline silicon generated in the process is typically small grained, of a random microstructure, and having a nonuniform grain sizes, therefore resulting in poor and nonuniform devices and accordingly, low manufacturing yield. Second, in order to obtain acceptable performance levels, the manufacturing throughput for producing polycrystalline silicon must be kept low. Also, the process generally requires a controlled atmosphere and preheating of the amorphous silicon sample, which leads to a reduction in throughput rates. Accordingly, there exists a need in the field to generate higher quality polycrystalline silicon at greater throughput rates. There likewise exists a need for manufacturing techniques which generate larger and more uniformly microstructured polycrystalline silicon thin films to be used in the fabrication of higher quality devices, such as flat panel displays.